1. Field of the Invention
The present invention relates to a cell voltage measuring device. More specifically, the present invention relates to a cell voltage measuring device which measures the cell voltage of a fuel cell.
2. Description of Related Art
FIG. 12 shows an example of conventional fuel cells which may be mounted in vehicles, such as fuel cell powered vehicles. In the fuel cell shown in FIG. 12, a plurality of cell units 95 are stacked, each of which includes a solid polymer electrolyte membrane 91 formed by, for instance, a solid polymer ion exchange membrane, sandwiched by an anode 92 and a cathode 93, and a pair of separators 94 and 94 holding the electrodes 92 and 93. Also, a fuel gas passage 96 which supplies a fuel gas (for instance, hydrogen gas), and an oxidant gas passage 97 which supplies an oxidant gas (for instance, air) are provided for each of the cell units 95.
In a fuel cell of this type, hydrogen ions generated at the anode 92 by a catalytic reaction move to the cathode 93 by passing through the solid polymer electrolyte membrane 91, and generate electric power at the cathode 93 by causing an electrochemical reaction with oxygen.
In a fuel cell having the above structure, it is necessary to control a power generation state of each cell unit 95 in order to detect abnormal cell units (i.e., malfunctioning or deteriorating cell units) as quickly as possible. For this reason, voltage (hereinafter referred to as cell voltage) of each cell unit 95 is measured.
In order to measure the cell voltage, the pair of separators 94 and 94 of each cell unit 95 are connected to a voltage detection circuit 101 of an electrical control unit (ECU) 100.
Japanese Unexamined Patent Application, First Publication No. Hei 9-283166 discloses a technique relating to a connection structure of a harness 102, which is connected to the voltage detection circuit 101, with the separator 94. In the connection structure described in the above publication, a hole used for attachment to a terminal is formed for each separator, and an output terminal provided with an end of each harness is inserted into the hole to make a connection.
Also, in another connection structure, an output terminal for measuring voltage is provided with a separator, and a connector is provided with an end of each harness so that the connector is connected to the output terminal of each of the separators.
However, in the former conventional connection structure, the output terminal must be inserted into the holes of the separator one by one to establish a connection, and in the latter conventional connection structure, the connector must be connected to the output terminal of each separator one by one. Accordingly, in the cell stack formed by stacking a few tens to a few hundreds of cell units 95, the connection process become very complicated for both of the two types of conventional connection structure, and there are problems in that errors in connection occur or a connection portion tends to be easily disconnected due to defective connection.
Also, since a harness which corresponds to each of the separators 94 is required in any of the conventional connection structures, the number of harnesses required becomes significant, and this is a drawback for decreasing the size and the weight of the device. Moreover, there is a problem in that each of the harnesses used may be tangled in a complicated manner.
Accordingly, an object of the invention is to provide a cell voltage measuring device for a fuel cell which enables an easy connection operation and reduction in the size and weight of the device by connecting a separator of the fuel cell with a voltage measuring means without using a harness.
In order to achieve the above object, the present invention provides a cell voltage measuring device for a fuel cell including a terminal member to be connected to a separator of the fuel cell, the terminal member including a first end and a second end, and a voltage measuring unit, such as a control unit which measures cell voltage of the fuel cell through the terminal member, wherein the first end, such as a base portion, of the terminal member is fixed to the voltage measuring unit, and the second end, such as a connection portion, of the terminal member makes contact with the separator, and an elastic portion, such as a spring arm is provided between the first end and the second end of the terminal member.
According to the cell voltage measuring device described above, since the terminal member and the separator can be connected without using harness, the connection process becomes easy, and the size and weight of the device can be decreased. Also, since the positional error between the terminal member and the separator to which the terminal member makes contact can be absorbed by the elastic portion, it becomes possible to securely contact the terminal member with the separator during the assembly. Moreover, when the separator is displaced due to heat generated by the fuel cell in the stacking direction thereof, the displacement can be absorbed by the elastic portion so as to prevent an excessive load from being applied to the terminal member. Accordingly, it becomes possible to prevent the terminal member from being damaged.
In accordance with another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a terminal cover, which covers at least a part of the terminal member.
According to the above cell voltage measuring device, since it becomes possible to avoid foreign materials, such as water, attaching to the terminal member, electrical shorts among the terminal members can be prevented. Therefore, the reliability of the cell voltage detection can be improved.
In yet another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a holder member, which is capable of maintaining a state in which the second end of the terminal member is separated from each other, wherein the holder member is movably attached in a stacking direction of the separator with respect to the voltage measuring unit.
In yet another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a holder member, which is capable of maintaining a state in which the second end of the terminal member is separated from each other, wherein the holder member is movably attached to the terminal cover in a stacking direction of the separator with respect to the voltage measuring unit.
In yet another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a holder member, which is capable of maintaining a state in which the second ends of the terminal members is separated from each other, wherein the holder member is attached to the voltage measuring unit in a movable manner in a stacking direction of the separator with respect to the voltage measuring unit.
According to the above cell voltage measuring device, it becomes possible to make the second end of the terminal member follow the movement of the separator in the stacking direction while maintaining the electrically separated state of the second end of the terminal members. Accordingly, generation of electrical shorts among the terminal members can be assuredly prevented even when the second ends of the terminal members are displaced in the stacking direction of the separator, and the reliability of cell voltage measurement is improved.
The present invention also provides a cell voltage measuring device, such as a cell measuring device, for a fuel cell including a terminal member to be connected to a separator of the fuel cell, the terminal member comprising a first terminal portion and a second terminal portion, and the second terminal portion including a first end, such as a coupling portion, and a second end, such as a connection portion and a voltage measuring unit (for instance, a control unit 31 in the second embodiment described later) which measures cell voltage of the fuel cell through the terminal, wherein the first terminal portion is fixed to the voltage measuring unit, and the first end of the second terminal portion is rotatably supported by the first terminal portion, and the second end of the second terminal portion makes contact with the separator, and an elastic portion, such as a spring arm 45 is provided between the first end and the second end of the second terminal portion.
According to the above cell voltage measuring device, excellent effects can be obtained in that the second terminal portion can be easily contacted or separated from the separator by rotating the second terminal portion with respect to the first terminal portion. Also, since the second terminal portion can be contacted to the separator without using the harness, the connection operation becomes easy and the size and weight of the device can be decreased. Moreover, since the positional error between the second terminal portion and the separator to which the second terminal portion makes contact can be absorbed by the elastic portion, it becomes possible to securely contact the second terminal portion with the separator during the assembly. Further, when the separator is displaced due to heat generated by the fuel cell in the stacking direction thereof, the displacement can be absorbed by the elastic portion so as to prevent an excessive load from being applied to the first terminal portion and the second terminal portion. Accordingly, it becomes possible to prevent the first terminal portion and the second terminal portion from being damaged.
In accordance with another aspect of the invention, the above cell voltage measuring device for a fuel cell further includes a terminal cover which covers at least a part of the terminal member.
According to the above cell voltage measuring device, since it becomes possible to avoid foreign materials, such as water, attaching to the terminal member, and electrical shorts among the terminal members can be prevented. Therefore, the reliability of the cell voltage measurement can be improved.
In yet another aspect of the invention, the above cell voltage measuring device for a fuel cell further includes a holder member which is capable of maintaining a state in which the second ends of the second terminal portions are separated from each other, wherein the holder member is movably attached in a stacking direction of the separator with respect to the voltage measuring unit.
In yet another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a holder member which is capable of maintaining a state in which the second end of the second terminal portion is separated from each other, wherein the holder member is attached to the terminal cover in a movable manner in a stacking direction of the separator with respect to the voltage measuring unit.
In yet another aspect of the invention, the cell voltage measuring device for a fuel cell further includes a holder member which is capable of maintaining a state in which the second end of the terminal is separated from each other, wherein the holder member is attached to the voltage measuring unit in a movable manner in a stacking direction of the separator with respect to the voltage measuring unit.
According to the above cell voltage measuring device, it becomes possible to make the second end of the second terminal portion to follow the movement of the separator in the stacking direction while maintaining the electrically separated state of the second end of the second terminal portions. Accordingly, generation of electrical shorts among the terminal members can be assuredly prevented even when the second end of the second terminal portions are displaced in the stacking direction of the separator, and the reliability in cell voltage detection is improved.